Solenoid actuator

ABSTRACT

A solenoid actuator having a core which can be attracted to either of two extreme positions in a housing by separately energized, longitudinally spaced coils and at least one relatively rotatable shaft protruding from the core. Springs mounted between the core and interior walls of the housing are compressed when the core is attracted to an extreme position. When an adjacent coil is de-energized, the compressed spring pushes the core toward the other extreme position. An electromagnetic field established by simultaneously energizing the other coil attracts the spring-propelled core to the other extreme position. Spring forces and electromagnetic forces complement one another, resulting in a high speed, long throw actuator with low electrical power requirements.

United States Patent [191 Markowitz et al.

[ Jan. 8, 1974 [22] Filed:

[ SOLENOID ACTUATOR [75] Inventors: Ivan N. Markowitz, Oklahoma City;

Darby A. Gray, Norman, both of Okla.

[73] Assignee: Honeywell Information Systems Inc.,

Waltham, Mass.

July 19, 1972 [21] Appl. No.: 273,092

521 US. Cl. 335/266, 335/268 [SI] Int. Cl. 1101f 7/08 [58] Field of Search 335/256, 257, 258, 335/266, 268, 274

FOREIGN PATENTS OR APPLICATIONS 84.878 1/1955 Norway 335/266;

Primary ExaminerGeorge Harris 7 Attorney-Gerald R. Woods 57 ABSTRACT A solenoid actuator having a core which can be attracted to either of two extreme positions in a housing by separately energized, longitudinally spaced coils and at least one relatively rotatable shaft protruding from the core. Springs mounted between the core and interior walls of the housing are compressed when the core is attracted to an extreme position. When an adjacent coil is de-energized, the compressed spring pushes the core toward the other extreme position. An electromagnetic field established by simultaneously energizing the other coil attracts the spring-propelled core to the other extreme position. Spring forces and electromagnetic forces complement one another, resulting in a high speed, long throw actuator with low electrical power requirements.

2 Claims, 3 Drawing Figures SOLENOID ACTUATOR BACKGROUND OF- THE INVENTION The present invention relates to electromagnetic devices and more particularly to a solenoid actuator which uses mechanical and electromagnetic forces in complementary fashion to control core movement.

Different types of solenoid actuators have been developed in efforts to obtain a long stroke, high speed linear actuator. One known type is a high power solenoid which achieves high speed operation by means of a heavy return spring. The electrical power required to accelerate the core from its rest position and to overcome opposing forces exerted by the heavy return spring limits the duty cycle of this type of solenoid to extremely low levels.

Another type of prior art actuator uses a voice coil arrangement to achieve high speed operation. Voice coil actuators are relatively expensive and bulky. Further, because the number of turns in the voice coil is kept small to keep the air gaps small, the power requirement for a voice coil actuator is high and the allowable duty cycle is low.

Still another prior art solenoid actuator uses levers for mechanical advantage. It is quite difficult to obtain linear motion with this type of actuator because of play in the pivots between the levers. This type of actuator is bulky and is subject to excessive wear and early failure.

SUMMARY OF THE INVENTION The present invention is a long stroke, high speed, linear solenoid actuator having relatively low electrical power requirements. These characteristics are obtained by using mechanical or spring forces and electromagnetic forces in complementary fashion to control core movement.

An actuator constructed in accordance with the present invention includes a housing including a central cavity and a pair of smaller openings extending through opposite walls of the housing. A core assembly is movable within the housing between two extreme positions on the axis of the opening. This core assembly consists of a central core member and two shaft members, at least one of which is rotatable relative to the central core member. A first energizable means can draw the core assembly to and hold it in one of the two extreme positions. A second energizable means can draw the core to and hold it in the other of the two extreme positions. Coil springs are positioned on the shafts for urging the core assembly from the extreme positions toward a range of unbiased positions intermediate the two extreme positions. The forces exerted by the springs are insufficient to overcome forces which can be exerted by the energizable means.

DESCRIPTION OF THE DRAWINGS While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, details of a preferred embodiment of the invention maybe more readily ascertained from the following detailed description when read in conjunction with the accompanying drawing wherein:

FIG. 1 is a cross-sectional view of a solenoid actuator constructed in accordance with the present invention;

FIG. 2 is a perspective view of the solenoid actuator of FIG. 1 for use in explaining the operation of the ac tuator; and

FIG. 3 is a cross-sectional view of one embodiment of the core assembly of the solenoid actuator.

DETAILED DESCRIPTION Referring now to FIG. 1, a housing It) for a solenoid actuator constructed in accordance with the present invention preferably includes an upper housing 12 and a lower housing 14. The upper housing 12 includes an energizable means such as a toroidal coil 16 wrapped on a coil support 18. The toroidal coil 16 can be energized through a pair of electrical leads 20 extending from the right side of housing 10. The lower housing 14 contains a similar toroidal coil 22 wrapped about a coil support 24. Toroidal coil 22 can be energized independently of toroidalcoil 16 through electrical leads 26. The upper housing 12 and lower housing 14 are connected at an interface which includes a flux permeable toroidal pole 28.

The assembled housing 10 defines a longitudinal opening including a cnetral cavity 30 and smaller openings 32 and 34 near the top and bottom surfaces of the housing 10. A core assembly located in the longitudinal opening includes a large central core member 36 to which a first shaft 38 and a second shaft 40 may be attached. The central core member 36 and the shafts 38 and 40 are movable along a linear path defined by the interior walls of the longitudinal opening to either of two extreme positions. The first extreme position is one in which a shoulder 42 on the upper end of the core member 36 is seated against a conical surface 44 at the upper end of the central cavity 30. The second extreme position is illustrated in FIG. 1. In this second extreme position, a shoulder 46 at the lower end of central core member 36 bears against a conical surface at the lower end of central cavity 30.

The solenoid actuator also includes biasing means which preferably consists of a first coil spring 48 surrounding a sleeve 50 on shaft 38 and a second coil spring 52 surrounding a sleeve 54 on shaft 40. The first and second coil springs 48 and S2 tend to bias the central core member 36 from the extreme positions to a range of unbiased positions within the central cavity 30.

The operation of the device described above is explained with reference to FIG. 2. When the toroidal coil 22 in the lower housing 14 is energized by applying current to the electrical leads 26, a flux is established along a path 56 which attracts the central core member 36 downwardly to the lower extreme position wherein coil spring 52 is compressed between the lower face of core member 36 and the interior wall of lower housing 14. The central core member 36 can be maintained at the lower extreme position against the opposing force of compressed coil spring 52 by means of a relatively low holding electrical current.

When the core assembly is to be moved from the lower extreme position to the upper extreme position, toroidal coil 22 is de-energized and toroidal coil 16 in the upper housing 12 is energized. Mechanical forces generated by expanding coil spring 52 propel the core assembly upwardly. Flux directed along a path 58 by the energized toroidal coil 16 produces an electromagnetic field which captures the moving core assembly and causes it to be seated against the conical surface 44 in the housing 12. Coil spring 48 is, of course, compressed between the upper end of core member 36 and the interior wall of upper housing 12 as core member 36 becomes seated. The core assembly can be held in the upper extreme position against the force of the now-compressed coil spring 48 by applying a low holding current to the toroidal coil 16.

A solenoid actuator constructed as described is an extremely efficient device. The primary electrical power requirement, occurring when the core assembly is being seated against the opposing force of a compressing coil spring, is low since the air gap during seating is small. Moreover, since most of the force required to accelerate the core assembly from one extreme position toward the other is obtained in the release of mechanical force by the expanding coil springs, a smaller magnetic path can be used thereby reducing the required size and weight of the overall solenoid actuator. The use of mechanical or spring forces and electromagnetic forces in complementary fashion allows the core assembly to move through a long stroke without the need for a strong magnetic field to accelerate core assembly from a rest position. By choosing the proper spring rate and applied current, an actuator constructed as described can be made to operate at a very high speed with an almost constant force during movement from one extreme position to the otherL Moreover, the symmetry of the solenoid actuator construction lends itself to applications where uniform bidirectional operation characteristics are required.

The linearity of the path traversed by the core assembly 36 and the shafts 38 and 40 is controlled by the sleeves 50 and 54 and the inner surfaces of the coil supports 18 and 24 which, if made from certain materials, act as low friction bearing surfaces for the surface of the central core member 36. The dual functions served by the coil supports reduce the cost of solenoid actuators constructed in accordance with the present invention.

In some applications, it is desirable to have one or both of the shafts 38 and 40 rotatable relative to the remainder of the solenoid actuator. FIG. 3 shows one possible arrangement for providing this rotational capability with low rotational inertia. Shaft 38 is decoupled from the core member 36 through a bearing set 60 within the core member 36. The shaft 38 becomes a low inertia load since it is decoupled from and therefore unaffected by the rotational inertia of the relatively heavy core member 36.

While there has been described what is believed to be a preferred embodiment of the present invention, variations and modifications will occur to those skilled in the art once they become familiar with the invention. Therefore, it is intended that the appended claims shall be construed as covering all such variations and modifications as fall within the true spirit and scope of'the invention.

What is claimed is:

l. A solenoid actuator comprising:

a. a housing having a longitudinal opening therethrough, the opening comprising a central cavity and a pair of smaller openings extending from the central opening through opposite walls of said housing;

b. a core assembly including 1. a central core member positioned within the central cavity for movement between two extreme positions on the axis of the longitudinal opening; and

2. first and second shaft members secured to said central core member for movement through the smaller openings, at least one of said shaft members being mounted for rotational movement with respect to said central core member;

c. a first energizable means for drawing said core assembly to one extreme position when energized; d. a second energizable means for drawing said core assembly to the other extreme position when energize'd;

e. a first coil spring positioned on said first shaft member at the one extreme position, said first spring member being compressed between said central core member and the housing when said central core member is drawn to the one extreme position; and

f. a second coil spring positioned on said second shaft member at the other extreme position, said second spring member being compressed between said central core member and the housing when said central core member is drawn to the other extreme position.

2. A solenoid actuator comprising:

a. a housing having a longitudinal opening therethrough, the opening comprising a central cavity and a pair of smaller openings extending from the central opening through opposite walls of said housing;

b. a core assembly including l. a central core member positioned within the central cavity for movement between two extreme positions on the axis of the longitudinal opening; and

2. first and second shaft members secured to said central core member for movement through the smaller openings, at least one of said shaft members being mounted for rotational movement with respect to said central core member;

c. a first electromagnetic coil encircling said core assembly for drawing said assembly to one extreme position when energized;

d. a second electromagnetic coil encircling said core assembly means for drawing said assembly to the other extreme position when energized;

e. a first coil spring member positioned on said first shaft member at the one extreme position, said first spring member being compressed between said central core member and the housing when said central core member is drawn to the one extreme position; and

. a second coil spring member positioned on said second shaft member at the other extreme position,

said second spring member being compressed between said central core member and the housing when said central core member is drawn to the other extreme position. 

1. A solenoid actuator comprising: a. a housing having a longitudinal opening therethrough, the opening comprising a central cavity and a pair of smaller openings extending from the central opening through opposite walls of said housing; b. a core assembly including
 1. a central core member positioned within the central cavity for movement between two extreme positions on the axis of the longitudinal opening; and
 2. first and second shaft members secured to said central core member for movement through the smaller openings, at least one of said shaft members being mounted for rotational movement with respect to said central core member; c. a first energizable means for drawing said core assembly to one extreme position when energized; d. a second energizable means for drawing said core assembly to the other extreme position when energized; e. a first coil spring positioned on said first shaft member at the one extreme position, said first spring member being compressed between said central core member and the housing when said central core member is drawn to the one extreme position; and f. a second coil spring positioned on said second shaft member at the other extreme position, said second spring member being compressed Between said central core member and the housing when said central core member is drawn to the other extreme position.
 2. first and second shaft members secured to said central core member for movement through the smaller openings, at least one of said shaft members being mounted for rotational movement with respect to said central core member; c. a first electromagnetic coil encircling said core assembly for drawing said assembly to one extreme position when energized; d. a second electromagnetic coil encircling said core assembly means for drawing said assembly to the other extreme position when energized; e. a first coil spring member positioned on said first shaft member at the one extreme position, said first spring member being compressed between said central core member and the housing when said central core member is drawn to the one extreme position; and f. a second coil spring member positioned on said second shaft member at the other extreme position, said second spring member being compressed between said central core member and the housing when said central core member is drawn to the other extreme position.
 2. A solenoid actuator comprising: a. a housing having a longitudinal opening therethrough, the opening comprising a central cavity and a pair of smaller openings extending from the central opening through opposite walls of said housing; b. a core assembly including
 2. first and second shaft members secured to said central core member for movement through the smaller openings, at least one of said shaft members being mounted for rotational movement with respect to said central core member; c. a first energizable means for drawing said core assembly to one extreme position when energized; d. a second energizable means for drawing said core assembly to the other extreme position when energized; e. a first coil spring positioned on said first shaft member at the one extreme position, said first spring member being compressed between said central core member and the housing when said central core member is drawn to the one extreme position; and f. a second coil spring positioned on said second shaft member at the other extreme position, said second spring member being compressed Between said central core member and the housing when said central core member is drawn to the other extreme position. 